Did You Say Quad Rate DSD?
The exaSound e20 MK III DAC can handle PCM, DXD, and DSD up to 12.288 MHz (256Fs) on Windows PCs. Mac users max out at the more or less typical DSD 128. While you'd be hard pressed to find any DSD downloads at DSD 256 (or even DSD 128), you can rest assured that the e20 can handle just about any file format you care to throw at it. The e20 also throws in on-DAC-chip volume control, single ended and balanced outputs, asynchronous USB, Coax, and Toslink inputs, and a headphone amp making it one all-around amenable DAC package.

You'll notice the left and right outputs are reversed from their typical setting

Handling D/A conversion duties is the ESS ES9018 Sabre32 reference DAC. This DAC also incorporates a volume control which is what exaSound has tapped into for the e20's. Three precision crystal oscillators are used to support the 44.1kHz family (44.1, 88.2, 176.4, and 352.8 kHz) and the 48kHz family (48, 96,192 and 384kHz), while the third oscillator "provides reference master clock with 0.13ps precision for D to A conversion." The Coax S/PDIF input can handle PCM resolutions up to 192kHz, the Toslink tops out at 96kHz, leaving the mini USB Type-A input handling all the heavy lifting up to 384kHz for PCM, DXD, and DSD. exaSound recommends using the USB input which makes perfect sense as its the only way to get the most out of the e20. All of these connections are around the backside of the e20 where you'd expect to find them along with the RCA and XLR outputs and the barrel IEC inlet for the included external laptop style power supply.

I asked George Klissarov, the President of exaSound Audio Design, about the functions the Xilinx FPGA is performing as well as what digital filter(s) the e20 employs:

The FPGA core is performing all the signal processing. The display and the general operation of the device is controlled by a small processor located on a separate board. This way the general computing noise is isolated in another subsystem.

The FPGA always works in bit-perfect mode. In other words, it is optimised for realistic reproduction of the sound, not for "enhancing", or "coloring", or making it "more musical". In my view DSP processing and up-sampling belong to the player application, because software is much easier to upgrade. We provide stable and transparent foundation, and users can put on top of it as much processing as desired. Another benefit of this approach is that since the e20 is not coloring the sound, it enhances the character of the system in use. If you have a tube amplifier, you will experience more of its specific sound because of the extra dynamic and resolution.

The 32bit signal path helps to preserve the maximum usable resolution of any DSP computations performed by the player application. There is no point to go for 64bit interface and FPGA processing with the current 32bit DAC chips. The limiting factor at this point is the DAC chip, and we believe we are using the most advanced one.

Going back from the DAC chip, the FPGA, the USB interface and the drivers are not limiting in any way the end result. The entire system, all the technologies on the signal path are developed in-house for the purpose of being as transparent as possible.

I am sorry, I can't comment on the digital filters. This is an area of proprietary development, and it is also related to our ability to achieve DSD256. We squeeze every bit of resource and performance available from the DAC chip, so there is no room left to provide user-controllable filter settings. In the future we may be able to allow for some user-selectable filter options.

The exaSound e20 requires drivers for both Mac and PC users which are available from the exaSound website. I downloaded and installed both versions as I used the e20 with my PC and Mac. Installation was very straight forward on both computers and I used Audirvana on the Mac and JRiver on the PC to control playback. If you have any DSD 256 source files, you'll need to play them back through a PC. Mac's max out at DSD 128.

The e20 MKIII v MKII
The e20 MKII can also playback up to quad rate DSD (DSD256 - Windows only), DXD, and up to 384kHz PCM files. The MKIII adds the ability to play back 3.072 MHz (64Fs) DSD, 6.144 MHz (128Fs) DSD, and 12.288 MHz (256Fs) DSD on Windows-based machines. Mac users are left with the standard 2.8224 MHz (64 Fs) and 5.6448 MHz (128 Fs) DSD capability. I also asked George Klissarov about these sample rates and also about any other differences between the MK II and MK III versions of the e20:

The first one is the ability to play DSD sampling rates that are multiples of the 48kHz PCM format. This feature came as request from users on the ComputerAudiophile.com forum. People are interested in real-time conversion/up-sampling of PCM files to DSD. This can be done offline, or in real time by using Foobar with the foo_input_sacd.dll. Conversion/up-sampling can also be done with the HQ Player. Both options are not very user friendly, but that's the price you pay for being on the leading edge. The new sampling frequencies are required for the proper conversion of 48, 96 and 192 kHz files.

To some extent the request for DSD with 48kHz base was to challenge us like "...you can do DSD at 11.2 MHZ, but can you do it at 12.3 MHz?". Immediately after we did it we received comment like "...who needs that?"...We honestly try to innovate in a rational and scientific way, and high sampling rates to me are a very credible way to experiment with improving the digital experience. If anything, this will make digital audio equal or better to analogue. As someone said, "Analogue is digital with infinite sampling rate". I believe DSD256 is getting remarkably close to infinite. We haven't seen the full potential of this format. Recording engineers need to learn how to use this tool. Other technologies like mastering software and microphones need to evolve.

The second improvement that comes with e20 Mk III is the ability to use an upgraded master clock. We haven't released this feature officially. We are collecting feedback and there is only a comment about it on the specifications page. So far the reaction is very positive, and we will make it official soon. For now it can be ordered only with email request, and during the test period we charge a symbolic $100. The upgraded clock has improved jitter rating - 0.082ps, or 82fs, compared to the 0.13ps for the standard clock. You see that we are getting into improvements that are expressed with numbers are so far from the decimal point, that it is becoming hard to measure the results. That's why we are doing the field testing. We don't want to be accused again of unnecessary chasing of numbers.

At the end of the day the subjective test matters, but at the same time the numbers and the measurements are needed to distinguish innovation from believing in magic.

Everything else about the MKII and MKIII are identical according to the exaSound specifications (see specs). When you download the exaSound drivers, you'll notice that there are two options; (2) channel or (8) channel. exaSound also makes the e28 multi-channel DSD DAC and you can read all about it from Kal Rubinson over on Stereophile.

Paint by Numbers
If you're expecting me to wax lyrical about the benefits of quad-rate DSD, as we say in Jersey faggetaboutit (I don't know anyone who actually says that unless they're not from Jersey but want to sound like they are). I'm not really a number lover and I find music to be more appealing. And it appears that the folks as exaSound share these sentiments seeing as the e20 DAC makes some beautiful music with all of the current formats you can actually buy.

I have a number of 'reference' recordings that I play on every single piece of gear that comes through here. "You must really like that song!" our daughter exclaimed exasperated when she heard Don Cherry's "Bemsha Swing" from Art Deco (CD rip) careening off my walls for the umpteenth time. And I do, still, like that song. I also like the way it shows off a components ability to handle acoustic bass, pocket trumpet which is a real stress test for the upper registers, sax, and a nice shimmery and full drum kit. And the e20 passed the Bemsha Swing test with flying colors. Literally. So many digital products seem to strip away layers of timbre, trading perceived detail in its stead. Not so with the exaSound. You get gobs of resolution, something the ESS DACs are known for, coupled with a very nice helping of tone color. While I've heard more bountiful bass reproduction and more apparent weight overall, my guess is, and its really a guess, a fitter power supply may just make up for this rather small deficiency.

exaSound's George Klissarov provided me with one 11.28MHz (DSD 256Fs) file of live solo violin music which I played back using my PC equipped with the SOtM tX-USBexp card (see review) and the voilin's sound was as sweet as I've heard in digital form. I'd imagine most people roughly my age who came of age when CDs first hit the market (OK I may have came of age a little sooner) can recall with a cringe what early digital did to violins and it wasn't pretty. Thin, shrill, and bleached is no way to go through life and thankfully we're beyond that now and I'd suggest that DSD in general, even regular old (smile) single rate DSD offers some of the sweetest upper registers around.

The e20 also acquitted itself very nicely with Altre Follie from Jordi Savall and Hesperion XXI on Archiv Music (also from a CD rip) playing works from 1500-1750 on instruments including Bass Viola da gamba, Triple Harp, and Harpsichord. The complex harmonics resounded in a very natural splash of tone, texture, and color. This recording can sound thin which gets old real fast but the e20 breathed a nice acoustic life into its sound making for an engaging performance. While I've heard more air in and around instruments, the e20 offered a very nice concise and richly resolute presentation.

Of course I listened to some DSD downloads from Channel Classics and Acoustic Sounds including Penderecki, Santana, Miles, and Ali Akbar Khan and I was treated with that sensuous round sound that DSD seems to convey so well. By comparison, the Auralic Vega DAC (see review) offered a bit more dimensionality and sparkle where sounds sound as if they're originating in a more believable 3-dimensional space. The e20 was tad flatter in comparison. The Mytek Stereo192-DSD DAC (see review) also sounded a bit more lit up making the e20 sound softer and a touch darker comparatively.

Using JRiver's DSP settings, I also listened to a few PCM tracks converted to double rate DSD. These kinds of comparisons strike me as being largely of the who cares variety since you'll only experience this if you have the e20 DAC and JRiver and the overall sound and character of the e20 is infinitely more important. That being said, if I owned the e20, I'd be very tempted to set JRiver to convert everything to double rate DSD. There's a slight softening to the presentation, coupled with a more dimensional quality that I find to be more engaging. With the PCM version left as PCM, there's a bit more sparkle up top coupled with a flatter sound. Pick your poison, its free.

I also took the e20's headphone output for a sonic spin, which also mutes the line level output as you'd expect, with my Audio Technica ATH-W1000s and found the overall sound to be on the dry side, drier than the sound through my DeVore The Nines. I'd attribute this as much to my headphones as to the e20 DAC but if you like your headphone listening to be on the fat, wet, and lush side, you may find that the e20 comes up short. What you get instead is a nice lean, light, and fast sound.

The mini USB input may give some cable aficionados pause as they won't be able to use their favorite USB cables without a USB to micro adapter. I will also note that overall I find the e20's build quality to be just fine which is fine but not exactly what I expect considering the e20s price tag. The little clear rubber feet stuck to the unit's bottom may strike some buyers as a corner that should not have been cut so close. I'd also suggest that the sonically equivalent e20 MK II for $400 less than the MK III may be worth a look for Mac users since they cannot make use of the MK III's higher DSD sample rates as well as Windows users willing to forgo the ability to convert 48kHz PCM and its multiples to their quad-rate DSD equivalent. The MK II also eliminates the upgraded clock option.

Music by the Numbers
Forget about numbers. The exaSound e20 DAC makes some fine music with all of the music your likely to get a hold of. CD-quality recordings sounded just lovely and higher resolutions sounded even lovelier. DSD strikes me as having a sound all of its own which is in a word rounder and more fulsome and the e20 did a fine job delivering those qualities. I also used the e20's volume control and found that it did not degrade the quality of reproduction to a noticeable degree even at lower volumes so those looking to do away with a preamp while keeping a healthy helping of their PCM, DXD, and DSD music's goodness will be well served by the exaSound e20 DAC.

A great review, glad to see the news spreading about these awesome DACs. The E28, using almost the same core design but having 8 output channels, really opens up some doors for playback of multichannel music, including multichannel DSD.

One clarification: ExaSound are not only direct. They do have a few dealers, such as ourselves (Acoustic Frontiers). Our added value is ability to provide not just the DAC but to support end users in setting up a media server for themselves. We are quite far along in terms of ability to support implementation of advanced capablities such as room correction using Dirac Live or setup of active crossover on the JRiver platform.